Depending on how well you know the girl should determin how you go about asking her to the dance.

If you know the girl very well and you get along great then it shouldnt be a problem, dont skip around the issue at hand, just let her know how u feel.

As an example, something basic like. "You know how the dance is coming up, well i was just wondering if you would be interested in going with me?"

I know at times it can be hard to find the right moment to ask or say it but in some cases it will never come, so its best to just somehow get onto the topic and then ask.

And your question about where to look, its best to look into her eyes, but dont stare. If she looks into yours, dont look away, it shows you are adversive. Im not saying that you have to look into her eyes at every given second, but if you can catch her eyes and look at each other then for all i know you could kiss her if you wanted to. timing is everything.

Hope some of that helped.